1. Field of the Invention
This invention relates to a process for manufacturing solid electrochromic element to be used as various dimmers and displays, and to automotive dimmers for sun roof, side-watching window and glare-free mirror using said solid electrochromic element.
2. Description of the Related Arts
Solid-state light-emitting diode (LED) and liquid crystal display (LCD) are extensively used in the electronics and related industries as various types of display elements. Studies are now under way to put electrochromic (EC) element to practical use as a new type of display element having unique characteristics not to be expected from LED and LCD.
Electrochromic elements are those elements in which the electrochromic substances involved undergo a redox reaction when a voltage is externally applied, causing reversible changes in color or light transmittance.
Electrochromic substances may be roughtly divided into inorganic and organic materials. Typical examples are oxides of transition metals for the former and viologen derivatives for the latter, but many other compounds are being used in recent years.
In any of these cases, each element is basically composed of several kinds of electrochromic materials laminated one upon another and sandwiched by a pair of electrodes.
Of the many types of electrochromic element, solid electrochromic elements (in which all the layes involved are solid) are receiving special attention in terms of reliability, cost, and the wide range of application field.
Solid electrochromic element may be manufactured by various physical vapor deposition (PVD) processes, for example, by the vacuum deposition or sputtering process. Alternatively, the vacuum deposition and the sputtering processes are used in combination in some cases; thin film of electrodes, color-developing layers and ion-donating layer (each made of oxides of transition metals and the like) are laminated one upon another on a glass substrate, using separate apparatuses for the two processes.
These deposition processes, however, have many disadvantages. The vacuum deposition process suffers from low adhesion of deposited elements to the substrate and from difficulty in obtaining elements of high conductivity. The sputtering process is low in productivity because of the long time required for lamination. In addition, the resultant elements are liable to deterioration because of the increased temperature of substrate, and the adhesion of thin layers is also poor. The combination of the vacuum deposition process with the sputtering process has the disadvantage that semi-finished products have to be taken out from the treating apparatuses during manufacture. This not only results in lower productivity, but may lead to degraded element characteristics due to contamination of the surface of each layer with impurities in atmospheric air.
Recently sun roofs are frequently installed on motorcars for the purpose of giving a spacious and roomy feeling and of properly adjusting the lightness in the interior. FIG. 5 is a related-art sun roof composed of a roof section 62 made of steel and a glass section 63, in which the quantity of light that enters the interior is controlled by properly sliding said roof section 62 by manual operation or by the aid of a motor. Besides this, there is another type of sun roofs using a glass section with mesh print. The slide operation of the above-mentioned sun roof 61, whether it be manual or motor-driven, is a cumbersome work because it must be performed while observing the sun roof. In the mesh-type sun roofs, on the other hand, the quantity of entering light cannot be adjusted.
Large cars such as motortrucks have a side-watching window at the door near the driver's seat through which the driver can judge, when turning to the right or changing the lane, if any obstruction is present or not on the side (see FIG. 6). The larger the area of side-watching window, the more correctly will the driver be able to check the presence or absence of obstructions. An excessively large window, however, will disturb the driver because the road surface on the side and other objects also come in sight, and will pose the problem of possible invasion of driver's privacy because the interior of driver's cab is fully exposed to view.
As an example of glare-free, automotive mirrors (such as rearview mirrors), may be mentioned a prism mirror shown in FIG. 12, which comprises a transparent body 71 with its front and back faces being not parallel to each other, and a reflector layer 72 having a reflectance different from that of said transparent body 71 bonded thereto. When using this prism mirror 73 as a rearview mirror in the daytime, its mouting angle is adjusted so that the incident light will be reflected through the light path X in FIG. 12. When the strong light from the headlights of a succeeding car dazzles the driver's eyes in night driving, the dazzle of the light can be eliminated by changing the mounting angle of said prism mirror 73 so that the incident light will be reflected through the light path Y in FIG. 12.
Mirror angle control, however, is a cumbersome task for a working driver. A solution to this problem is a glare-free mirror using a transparent electrochromic element and utilizing the electrode layer on the back face of said electrochromic element as light-reflector layer. But a disadvantage of glare-free mirrors of this structure is that the color-developing layer of the electrochromic element is exposed to atmospheric humidity, making it difficult to exhibit its expected functions consistently over long periods. In addition, it is difficult to achieve an electrode that can function satisfactorily as light-reflector layer, because layers of smooth surface can hardly be obtained unless a very limited type of materials are used.